Control of charging in resonant tunneling through InAs nanocrystal quantumdots

Tunneling spectroscopy of InAs nanocrystals deposited on graphite was measu red using scanning tunneling microscopy, in a double-barrier tunnel-junctio n configuration. The effect of the junction symmetry on the tunneling spect ra is studied experimentally and modeled theoretically. When the tip is ret racted, we observe resonant tunneling through the nanocrystal states withou t charging. Charging is regained upon reducing the tip-nanocrystal distance , making the junction more symmetric. The effect of voltage distribution be tween the junctions on the measured spectra is also discussed. (C) 2001 Ame rican Institute of Physics.